1. Field of the Invention
The present invention relates to a lock mechanism applied to an electrical junction box which is mounted on an automobile or the like.
2. Description of the Related Art
In an electrical junction box which is mounted on an automobile, a lock mechanism integrally molded on each part is used to join molded parts of resin to each other. Japanese Patent Laid-open Publication No. 2002-354632 shows a lock mechanism provided for peripheries of an electrical component attachment block and a lower cover covering the bottom surface of the same.
This type of lock mechanism is often used for a part and a housing box accommodating the part. In this case, a lock arm including an engagement protrusion is integrally molded on the outer surface of a sidewall of the part. On the other hand, a lock protrusion which is engaged with the engagement protrusion is integrally molded on the inner surface of a sidewall of the housing box. As the part is inserted from above into the housing box, the lock arm is bent, and the engagement protrusion on the lock arm gets over the lock protrusion of the housing box. Eventually, the engagement protrusion and lock protrusion are locked to each other so that the part does not escape upward.
In the case where there is a need to prevent water intrusion from the outside like an electrical junction box mounted in an engine room, a waterproof structure is required. In this regard, the lock mechanism provided for resin molded products often includes a hole which can act as a water intrusion path because of the complicated shape thereof, molding reasons, and the like.